Implement custom plugpoints

Functionality in the XL Deploy server can be customized by using plugpoints. Plugpoints are specified and implemented in Java. On startup, XL Deploy scans its classpath for implementations of its plugpoints in the com.xebialabs or ext.deployit packages and prepares them for use. There is no additional configuration required.

The XL Deploy Server supports the following plugpoints:

  • Protocol: Specifies a new method for connecting to remote hosts.
  • Deployment package importer: Used to import deployment packages in a custom format.
  • Orchestrator: Controls how XL Deploy combines plans to generate the overall deployment workflow.
  • Event listener: Specifies a listener for XL Deploy notifications and commands.

For more information on Java API, see udm-plugin-api

Defining Protocols

A protocol in XL Deploy is a method for making a connection to a host. Overthere, the XL Deploy remote execution framework, uses protocols to build a connection with a target machine. Protocol implementations are read by Overthere when XL Deploy starts.

Classes implementing a protocol must adhere to the following requirements:

  • The class must implement the OverthereConnectionBuilder interface.
  • The class must have the @Protocol annotation.
  • Define a custom host CI type that overrides the default value for property protocol.

Example of a custom host CI type:

<type type="custom.MyHost" extends="overthere.Host">
  <property name="protocol" default="myProtocol" hidden="true"/>
</type>

The OverthereConnectionBuilder interface specifies only one method, connect. This method creates and returns a subclass of OverthereConnection representing a connection to the remote host. The connection must provide access to files (OverthereFile instances) that XL Deploy uses to execute deployments.

For more information, see the Overthere project.

Defining Importers and ImportSources

An importer is a class that turns a source into a collection of XL Deploy entities. Both the import source and the importer can be customized. XL Deploy includes a default importer that understands the DAR package format.

Import sources are classes implementing the ImportSource interface and can be used to obtain a handle to the deployment package file to import. Import sources can also implement the ListableImporter interface, which indicates they can produce a list of possible files that can be imported. The user can make a selection of these options to start the import process.

When the import source has been selected, all configured importers in XL Deploy are invoked, in turn, to determine if any importer is capable of handling the selected import source, using the canHandle method. The first importer that indicates it can handle the package is used to perform the import. The XL Deploy default importer is used as a fallback.

The preparePackage method is invoked. This instructs the importer to produce a PackageInfo instance describing the package metadata. This data is used by XL Deploy to determine if the user requesting the import has sufficient rights to perform it. If so, the importer’s importEntities method is invoked, enabling the importer to read the import source, create deployables from the package and return a complete ImportedPackage instance. XL Deploy will handle storing of the package and contents.

Defining Orchestrators

An orchestrator is a class that performs the orchestration stage. The orchestrator is invoked after the delta-analysis phase, before the planning stage, and implements the Orchestrator interface containing a single method:

Orchestration orchestrate(DeltaSpecification specification);

For example, this is the Scala implementation of the default orchestrator:

@Orchestrator.Metadata (name = "default", description = "The default orchestrator")
class DefaultOrchestrator extends Orchestrator {
  def orchestrate(specification: DeltaSpecification) = interleaved(getDescriptionForSpec(specification), specification.getDeltas)
}

It takes all delta specifications and puts them together in a single, interleaved plan. This results in a deployment plan that is ordered solely on the basis of the step’s order property.

In addition to the default orchestrator, XL Deploy also contains the following orchestrators:

  • sequential-by-container and parallel-by-container orchestrator. These orchestrators group steps deal with the same container together, enabling deployments across a collection of middleware.
  • sequential-by-composite-package and parallel-by-composite-package orchestrators. These orchestrators group together steps by contained package. The order of the member packages in the composite package is preserved.
  • sequential-by-deployment-group and parallel-by-deployment-group orchestrators. These orchestrators use the deployment group synthetic property on a container to group steps for all containers with the same deployment group. These orchestrators are provided by a separate plugin that comes bundled with XL Deploy inside the plugins/ directory.

Defining Event Listeners

XL Deploy sends events that listeners can act upon. There are two types of events in XL Deploy:

  • Notifications: Events that indicate XL Deploy has executed a particular action.
  • Commands: Events that indicate XL Deploy is about to execute a particular action.

Commands are fired before an action takes place, while notifications are fired after an action has taken place.

Listening for notifications

Notifications indicate a particular action has occurred in XL Deploy. Some examples of notifications in XL Deploy are:

  • The system is started or stopped.
  • A user logs into or out of the system.
  • A CI is created, updated, moved or deleted.
  • A security role is created, updated or deleted.
  • A task, such as: deployment, undeployment, control task, or discovery; is started, cancelled, or aborted.

Notification event listeners are Java classes that have the @DeployitEventListener annotation and have one or more methods annotated with the T2 event bus @Subscribe annotation.

For example, this is the implementation of a class that logs all notifications it receives:

import nl.javadude.t2bus.Subscribe;

import com.xebialabs.deployit.engine.spi.event.AuditableDeployitEvent;
import com.xebialabs.deployit.engine.spi.event.DeployitEventListener;
import com.xebialabs.deployit.plugin.api.udm.ConfigurationItem;

/**
 * This event listener logs auditable events using our standard logging facilities.
 **/
@DeployitEventListener
public class TextLoggingAuditableEventListener {

    @Subscribe
    public void log(AuditableDeployitEvent event) {
        logger.info("[{}] - {} - {}", new Object[] { event.component, event.username, event.message });
    }

    private static Logger logger = LoggerFactory.getLogger("audit");
}

Listening for commands

Commands indicate that XL Deploy has been asked to perform a particular action. Some examples of commands in XL Deploy are:

  • A request to create a CI or CIs has been received.
  • A request to update a CI has been received.
  • A request to delete a CI or CIs has been received.

Command event listeners are Java classes that have the @DeployitEventListener annotation and have one or more methods annotated with the T2 event bus @Subscribe annotation. Command event listeners have the option of reject a particular command which causes it to not be executed. Veto event listeners indicate that they have the ability to reject the command in the Subscribe annotation and veto the command by throwing a VetoException from the event handler method.

For example, this listener class listens for update CI commands and optionally vetoes them:

@DeployitEventListener
public class RepositoryCommandListener {

    public static final String ADMIN = "admin";

    @Subscribe(canVeto = true)
    public void checkWhetherUpdateIsAllowed(UpdateCiCommand command) throws VetoException {
        checkUpdate(command.getUpdate(), newHashSet(command.getRoles()), command.getUsername());
    }

    private void checkUpdate(final Update update, final Set<String> roles, final String username) {
        if(...) {
            throw new VetoException("UpdateCiCommand vetoed");
        }
    }
}